FIG. 1A depicts a frontal view of the skeletal structure forming the pelvic ring, and FIGS. 1B and 1C depict cross-sectional side views of the skeletal structure forming the pelvic ring. As shown in FIGS. 1A, 1B and 1C, the pelvic ring includes right and left ilium bones 105, 110, the sacrum 115 and their associated ligamentous connections. The main connections are through and around the right and left sacrociliac joints 120, 125 at the posterior of the pelvis and the pubic symphysis 130 at the anterior of the pelvis. The pelvic ring is a key structural element of the skeletal system because it is a weight-bearing structure interposed between the upper body and the legs. As such, if a fracture occurs and it is untreated, the pelvic ring may not heal (nonunion) or may heal in a poor position (malunion). Nonunion can lead to chronic pain and an inability to walk. Malunion can result in a short leg or one which points in the wrong direction. Because of these problems, it is necessary to reposition to normal the fragments which have become displaced during the fracturing (reduction). Once the fragments are repositioned, it is necessary to hold them in place (fixation) until the healing of the fracture is complete. This process may take approximately 6 to 8 weeks.
Because the pelvic ring forms a ring structure, it cannot be disrupted in one place when a fracture occurs. Typically, a disruption, or “break,” occurs in both the posterior and anterior portions of the pelvic ring. The disruptions in the pelvic ring can be through one or more of the bones 105, 110, 115, through the posterior sacrociliac joints 120, 125, through the pubic symphysis 130 at the front, or any number of combinations of the above. If the acetabulum (a portion of each ilium bone 105, 110 forming the hip socket) is fractured, the smooth bearing surface of the acetabulum must be restored to as close to its original shape as possible in order to allow for proper movement at the hip. Once restored, the acetabulum must be held in the restored position until healing occurs.
Conventional treatment of a pelvic fracture includes reduction of the fracture fragments and fixation with plates and screws along the surface of the bone. However, placing a plate on the bone requires a significant operation with resulting high blood loss. In some cases, a straight intramedullary screw may be placed along a curved path. While the screw is less invasive, the fixation may be inadequate because the straight screw cannot be implanted very far into a curved bone. This may result in inadequate fixation. Moreover, the screw must be relatively small in diameter to avoid extending through the bone. Surgically speaking, implanting a screw such that it extends from the bone can result in significant hazard to the patient because it may puncture or otherwise impinge upon important vascular and nervous structures.